Lathe apron mechanism



16 Sheets-Sheet 1 WILLIAM F. GROENE BY HARRY C. KEMPER ATTORNEY.

m o H i m w HE S H m a L u vmm m. n a: Wi mm +m a 5 H m9 mm a a Fm I x I0 AM n r r June 1939- w. F. GROENE ET AL LATHE APRON MECHANISM Filed May23, 1938 \MTNESS.

June 6, 1939. w. F. GROENE E'r AL LATHE APRON MECHANISM Filed May 25,1938 16 Sheets-Sheet 2 E El INVENTORS. my:

ATTORNEY.

June 6, 1939.

w. F. GROENE El AL LATHE APRON MECHANISM Filed May 23, 1938, 1eSheets-Sheet v6 INVENTORS. W'TNE/SS- aw:- W/p/M BY ATTORNEY.

-'June 6, 1939. I W4. IF.GROE'NE TEIIY-AL l f f 2,160,966 LATHEAPROVNMECHAXYIS'M Filed May 23,1938 H 1e Sheets-Sheet 7 INVENTORS.

wr ness. WILLIAM aqaoens" HARRY C.KEMPER ATTORNEY. v

June 6, 1939- w. F. GROENE ET AL LATHE 'APRON MECHANISM l6 Sheets-Sheet8 Filed May 25, 1938 INVENTORS. WILLIAM F. GROENE HARR BY Y C.KEMPERATTORNEY.

June 6, l939.= w. F. GROENE EI'AL LATHE APRON MECHANISM 16 Sheets-Sheet9 Filed May 25, 1938 SEE E 1M A A m BY wwa di /my June 6, 1939. w. F.GROENE ET AL 2,160,966

LATHE APRON MECHANISM Filed May 23, 1938 16 Sheets-Sheet 1O f INVENTORS.WITNES S v wmum FLGRQENE WW Puma ATTORNEY.

June 6, 1939.. w. F. GRoEN E ET AL LATHE APRON MECHANISM Filed May 23,1938 16 Sheets-Sheet ll wrmsss. fikpw iggg fldwanffiz g 6 BY EM ERKOMM'S.

ATTORNEY.

I June 6, 1939. I i w GRQQENE ET AL 2,160,966

LATHE APRON MECHANISM Filed May 25, 193 8 16 Sheets-Shee't l2 uu\mINVENTORS.

Qfiness. fwd 1 ER mm W E W G 0 F W N A AT R u wH June6, 1939. w. F.GROENE EI AL LATHE APRoN MECHANISM Filed Mayz23, 1958 16 Sheets-Sheetl3- INVENTORS. WILLIAM F GROENE BY HARRT C.KEMPE R mod-g.

WITNESS. I "fl/Jwxfli z ATTORNEYI" June 6, 1939. w. F. GROENE ET ALLATHE APRON MECHANISM Filed May 23/1938 l6 Sheets-Sheet l5 53 INVENTORS.m w\LL\AM mm WITNESS.- BY HARR -.KEMPER Wj/dy KQJZQMTS.

ATTORNEY.

June 6, 1939.

PEEK.

@JM 1 %L/ W. F. GROENE ET AL LATHE APRON MECHANISM Filed May 23, 1958 16Sheets-Sheet l6 wmmls ATTORNEY.

20 dered operative ineither direction. effort and skill on the part ofthe operator on 20 Patented June @1935 I I I UNITED STATES PATENT-OFFICEWilliam F. Groene and Harry 0. Kemper cincin nati, Ohio, asslgnors toThe R. K. Le Blond Machine Tool Company, Cincinnati, Ohio, a cornotationof Delaware Application any 23. 1938, Serial- No. 209.454 g 14 Claims.(cl. axe-2'2) This invention pertains to improvements in looking thepower cross feed mechanism witlisaid lathe apron mechanism, moreparticularly in cross stop mechanism whereby the latter is renlatheaprons of a character shown in co-pending dered inoperative whenever thepower cross teed application Serial No. 185,562 dated January 18, isrendered eflective to prevent damage to the 5 1938, and applicable tolathes of the character cross feed mechanism and the cross stop mecha 5shown in co-pending application Serial No. 84,500 nism in the event thecross feed should accidently -filed June 10, 1936, and Serial No.171.670 filed 'be' thrown in when the cross stop mechanism October 29,1937. was-being used.

One object of this invention is to improve the We also propose to havein'conjunction with sensitiveness and accuracy of control of the rapidthe above interlocking mechanism of the cross '10 traverse mechanism forthe longitudinal. and stop and the cross feed mechanism means whereecross travel of the lathe carriage and cross slide by the cross stopmechanism may be rendered by improving the various leveragesand linkagescompletely inoperative at times when no cross shown in the earlierapplication, Serial No. stop mechanism is desired. L

185,562. It is also our intention to provide'a unique 1,

Another object of this invention isto provide setting and lockingarrangement in connection means for automatically disengaging thelongiwith the dial indicating means above mentioned tudinal feed .handwheel for the carriage actuwhe y Single d S n Operations m y be ationwhen the rapid traverse mechanism is renndertaken o hese ia s W a u ofAnother object is to provide in connection with setting them to th irdesired position. thelongitudinal feed hand wheel, dial indicating Andit is also a feature of our invention to mechanisms showing the totaldistance of travel P ide qu ck et St p do s on t e control rod of thelathe carriage in'inches and in thousandths for the feed reversemechanism which are actuof an inch on a pair of inter-related rotating aby t e o eme t of e arfia d lathe 5 graduated collars. apron along thebed of the lathe whereby a mini- Still another object of the inventionis topromum' of time is consumed in ma g these advide means whereby theabove mentioned dial justments for reversal of the carriage movementmechanism is connected with the longitudinal and for accuratelydetermining these reversal movement of the carriage and is at all timeseifeopositions for the carriage. and apro q the so tive to indicate theamount of said movement at e bed. whet er the carriage be operatedmanually by .The above features will be described in detail 'powerfeeding means, or power rapid traver e and additional features will bepointed out in the actuation. following description. 3 It is also ourintention 'to provide'dialindin t e drawings! eating mechanism with thecross feed screw for F e I is a f on v n of a he'T Dr indicatingaccurately in inches and in thouembodying the features of 'ourinvention. sandths oif an inch the total travel effected in u e His aplan view P r y in Section 011 the.cross slide. the'line 11-11 of FigureI of the apron shown 4" In connection with the above dialindicatingdetached from the lathe carriage.

mechanism associated with the cross feed screw, Figure 111 is right hend elevation of t we also provide a unique cross stop arrangement latheapron 0n the line III-J11 of Figures I to facilitate thread chasingwhereby the cross nd slide maybe withdrawn from adeflnite cutting Fi urIV s a, v t al ans rs s cti n 4.1 position and. rapidly returned theretoin making through the p n 0n e of i v the various passes over the threadbeing chased ures I and II. in the lathe. Figure V is a verticaltransverse section through We have also'provided a unique arrangementthe apron on the line V-'V of Figures 1, H, whereby'actuation of thecross slide in conjuncv and VIII.

tion with the cross stop mechanism may be Figure V1 is a left hand endelevation of the 50 effected by means of the rapid' traverse operatinglathe apron on the line VI-VI of Figures I, II,

mechanism' or manually in both directions durand VIII. ing the threadchasing operation. v Figure VII is a vertical transverse section .Wealso have in mind in connection with'thls through the apron on thelineVII-VII of-Flgv unique cross stop arrangement means iorinterures I,II, VIII, and IX. I J

FigureVIII is an enlarged front elevation of the left hand portion ofthe apron on the line VII.IVIII of Figures VII and IX, particularlyshowing the rapid traverse mechanism.

Figure IX is a diagrammatic section through the apron on the line IX-IXof Figure VIII.

Figure X is a vertical section through the cross feed dial on the lineXX of Figures and XV.

Figure'XI is a vertical section through the apron and carriage on theline XI-XI of Figures X, XIII, XIV, and XV, showing the interlockingmechanism between the cross feed and cross stop apparatus. v

Figure XII is a vertical section through the cross feed screw on theline XII-2H1 of Figures In and XV, particularly showing the settingclamping arrangement for the graduated collar of the cross andlongitudinal feed dials.

Figure 1511 is a vertical section through the cross feed dial on theline XIIIXIII of Figures XI and XV.

Figure XIV is a vertical section through the cross feed .dial on theline XIV-XIV of Figures .XI and XV.

Figure XV is a section through the cross feed dial mn the line XV-XV ofFigures X, XIII, and XIV.

Figure .XVI is a fragmentary diagrammatic view of the peripheryof thegraduated collars of the cross feed dial.

Figure XVII is a vertical section through the' longitudinal feed dial onof Figure VII.

Figure XVIII is a fragmentary diagrammatic view of the periphery of thegraduated collars of the longitudinal feed dial.

Figure XIX is a vertical section through the longitudinal feed dial onthe line XIII-XIX of Figure VII.

Figure 2G; is a section through one of the quick-acting stops on thefeed reverse control rod on the line XXXX of Figure m.

. Figure XXI is a transverse cross section through the feed reversecontrol rod showing an end eleva-' tion of the quick-acting stop on theline XXI XIH of Figure XX.

This lathe apron is designed to operate with lathes of a character shownin co-pending application Serial Number 84,500 filed June 10, 1936,having feeding mechanism of a character shown in co-pending applicationsSerial Number, 171,760 filed October 29, 1937, and Serial Number 185,562filed January 18, 1938, particularly as related to the arrangement ofthe various control, rods at the front of the lathe bed.

The apron I is bolted to the carriage 2 by suitable screws 3, thecarriage 2 in turn being slidably the line XVI[XVII mounted on ways 4 onthe bed 48 as is usual for lathes. Referring particularly to Figures I,II, III, and IV, the apron I has the usual half-nuts 5 and 6 adapted toengage the lead screw I when thread cutting operations are beingperformed. These half-nuts are operated by the usual scroll cam 8 towhich the operating handle 9 is attachedj'substantially as disclosed inPatent Number 980,971, issued January 10, 1911. Associated with thisarrangement is the usual chasing dial I 0 mounted on a shaft I lrotatablyjournaled in the apron and having a worm wheel I2 engaging in.the threads of the lead screw I to facilitate proper engagement of thehalf-nuts with the lead screw when chasing threads.

Mechanism is provided in this lathe apron for operatively connectingeither the cross feed mechanism or longitudinal feed mechanism with thedriving means of the lathe, of a character substantially as describedand claimed in Patent Number 1,944,231, issued January 23, 1934. Thedriving power for operating the cross and longitudinal feed mechanism isderived from the feed rod I3 which is driven from the main driving motorfor thelathe by mechanism, for example, as shown in copendingapplications Serial Numher 84,500 filed June 10, 1936, and Serial Number171,760 filed October 29, 1937. This mechanism is arranged substantiallylike that shown in 00- pending application Serial Number 185,562 filedJanuary 18, 1938. In a boss I4 formed integral with the apron I isrotatably mounted the bevel gear I5, having a splined bore I6 into whichthe feed rod I3 slidably engages so that the bevel gear I5 maybe rotatedby the feed rod at all times whether the apron I is stationary or isfeeding longitudinally.

Noting particularly Figure V, the bevel gear I5 is adapted to drive amating bevel gear I! mounted on the shaft l8 journaled, at right anglesto the feed rod I3, in suitable bearings I9 and 20 carried in the frontwall 2| and rear wall 22 respectively of the apron I. these walls adriving pinion 23 is formed on the shaft I8 and is adapted to drive theshiftable middle gear 24, Figure II, which is securely keyed and pinnedto the shifter shaft 25. This shaft is journaled for both axial androtary movements in suitable bearings 26 and 21 provided in therespective walls 2| and 22 of the apron 'I. the front of the shiftablegear 24 the front outer gear 28 is rotatably journaled on the shiftershaft 25 and is adapted to drive the cross feed screw 29 through thecross feed screw pinion 30 mounted on the cross feed screw- 29.

To the rear of the shiftable gear 24 is rotatably journaled on theshifter shaft 25 the rear outer gear 3|, which is adapted to drive thegear 32 mounted by slidable splined connection 33 on the rack pinionshaft 34. A feed control handle 35 for selecting and disengaging thecross or longitudinal feed is mounted on the axially slidable rock shaft36 which is appropriately mounted in the boss 31 formed integral withthe apron I, and has a toothed portion 38, Figures V and XIV, wherebythe shifter shaft may be axially moved for engaging the cross orlongitudinal feed substantially as disclosed in Patent 1,944,231.Interlocking means 39 between this mechanism and the mechanism foroperating the half-nuts is provided substantially as shown in Patent1,944,231. v

The splined rack pinion shaft 34, Figures 11 and IX, is journaled in asuitable anti-friction bearing 40 in the front wall 2| of the apron andis supported in an anti-friction bearing 4| in the rear wall 22. Theinner race of bearing 4| is secured to the shaft 34 by a suitable nut 42which holds the bearing firmly against the integral rack pinion '43formed on the shaft 34. The outer race of the anti-friction bearing 4|is adapted for axial movement in the bore 44 in the rear wall 22 and ina mating bore 45 in the gear 32. The shaft 34 is also adapted for axialmovement in the bearing 40. A pull knob 46 is fixed to the front end ofthe shaft 34 to facilitate manual movement of the rack pinion shaftaxially. The purpose of this is to enable the operator of, the lathe towithdraw the rack pinion 43 from the rack 41 fixed to the bed 48 whenusing the leadscrew and half nuts in thread chasing when it is desiredto avoid driving the various gear trains of the apron through the rack41 and pinion 43 when the apron Intermediate is being moved by the leadscrew i to prevent inaccuracies in the thread chasing and excessive wearof the lead screw and half nuts.

The handwheel 49 for manual longitudinal feeding ofthe carriage is fixedon shaft 59, Figures VII' and IX, which shaft is supported through thehub of the hand wheel 49 on the antifriction bearing 52 which'inturn iscarried by the cover plate 53 attached to the bracket 54 mounted t onthe front wall2| of the apronil. Mounted on bearings 55 and -56 in thefront and rear walls 2| and 22 of the apron l, coaxial with the shaft59, is the shaft 51 having. an integral pinion 58 formed thereon whichmeshes with the gear 92,

.so that rotationof the shaft 51 will cause the rack pinion 43 to berotated to move the carriage longitudinally. a r

Means are-provided, Figures VII and IX, for connecting or disconnectingthe handwheel 49 from, the-shaft 51 comprising a clutch collar 59 whichis axially slidable on the splined inner end so of the shaft 50,- thecollar 59'being adapted tion with a single lever control of a charactershown in application Serial Number 185,562 filed January 18, 1938 isprovided inthis apron. The

main source of driving power for the apron rapid traverse mechanism isderived. from the rapid traverse rod 62 which is driven at constantspeed .at all times during the operation of the lathe.

In the-boss 64, Figure IX, is journaled the bevel gear 65 on suitablebearings 66 adapted to prevent axial movement of the bevel gear 65. Thebevel gear 65 has a splined bore into which the rapid traverse rod 62slidingly engages, so that the bevel gear 65 may be rotated by the rapidtraverse rod 62 at all times whether the apron is stationary or isfeeding longitudinally. A mating bevel gear 61, adapted to be driven. bythe bevel gear 65, is formed'integrai with the shaft 68 which isjournaled perpendicular to the-rapid traverse rod 62 in suitableanti-friction bearings69 and which hearings in turn are mounted in thesleeve 1| secured in the rear wall 22, of the apron l. Mounted on theinner end of the shaft 68 and secured and held in driving relationthereon by the key I2 and lock nut 13" is a gear I4 adapted to engageand drive the gear I5 of the double gear 16, the compound gear. beingrotatably journaled on theshaft ll-fixed in the front wall 2| and rearwall 22' of the apron l. The gear also engages the'gear 18 of thecompound gear 19 which is journaled on the shaft 88 fixed in the frontwall 2| and rear wall 22 of the apron Thetraverse reverse and forwardfriction clutch assemblies are mounted on the shaft 8| which isjournaled in the antiefriction bearing 82 mounted in the rear wall 22and in the anti-friction bearing 83 slidably mounted in the bracket 54on the front wall of the apron l. The portion of the shaft 8|intermediate, these hearings. is provided with splines 84 upon which aremounted the clutch assemblies comprising the discs 85 and the gear. 86fitting in driving relation but adapted to axial movement on .thesplines 84. Rotatably journaied on the hubs 81 of the middle discs 85are the driving disc gears 88 and 88a to which are fixed appropriatecomposition friction material 89 adapted for frictional engagement withthe discs 85 and the side face of the gear 86. 7 Between these clutchassemblies is mounted the clutch operating member comprising the selfaligning ball bearing 90 having its inner race slidingly mounted on theperiphery of the shaft 8|. The clutch assembliesand operating member areproperly confined on the shaft 8| between the inner races of thebearings 82 and 83 by the adjustable bearing retainer 9| which engagesthe outer race of the bearing 83-and which may be easily adjusted forproperly setting the relative position of the clutch plates for properdriving engagement bymanipulating the adjusting screw 92 and lock nut93. It'can thus be seen thatas the clutch operating member 99 is urgedaxially toward the rear of the apron, the normally loose running discgears 88 .will be clamped between the associated discs 85 in drivingengagement with the shaft 8 I. Likewise the disc-gears 88:; may beengaged in driving relation with the shaft 8| when member 9|! is urgedtothe front of the apron The disc gears 88 are driven from the compoundgear I9 by means of the gear 94; and the disc gears 88a are driven fromthe compound gear 16 by means of gear 95.' It can therefore be seen thatsince the shaft 68 rotates at constant speed,

in the same direction by the means described, rotation of the disc gears'88 will therefore be produced through'the gears", I5, 18 and 94, whilerotation of the disc gears 88a will be produced through the gears 14,15, and95. It thus follows a that the disc gears" and 88a rotate inopposite directions and that by alternately engaging one or the'otherclutch assemblies by the appropriate axial movement of the member 90,corresponding directions of rotation in either direction can be producedin the shaft 8| and the gear 86. s

The mechanism for alternately connecting the a above forward and reverserapid traverse driving power to the longitudinal and cross travel of thecarriage and cross slide comprises the gear 86 which is adapted fordriving engagement with the axially slidable clutch gear 96 journaledfor free rotation'on the shaft 51, Figures VII and IX. When shiftedaxiallytoward the front of the apron I, the gear 96, which is at alltimes in driving engagement with the gear 86, meshes with a gear 91 ofthecompound gear 98 which compound gear is journaled. for free rotationupon a suitable extension 99 of the hub of the gear 32. The gear I08 ofthe compound gear 98 in turn is connected in driving relation with thegear 28, Figure II, which drives the cross feed mechanism as described.

The gear 96 has an internal clutch |0| adapted to engage over a portionI82 of the pinion 58 whereby to provide a positive driving connectionbetween the gear 96 and the pinion 58 so as to impart longitudinal rapidtraverse movements to the carriage through the gear 32 and rack pinion43 as described. It can thus be seen from the above description that thegear- 96 can be causes to rotate at rapid traverse speeds in either direternately applying rapid traverse motions in either direction to thelongitudinal and cross travel of the carriage and cross slide and inaddition mechanism whereby the hand wheel is automatically disengagedfrom the apron transmission when the rapid traverse control lever isactuated, particularly to prevent spinning of the carriage actuatinghand wheel when longitudinal rapid trave'rse movements are beingaffected. Referring to Figures I, II, VI, and VIII, the rapid traversecontrol lever I03 is conveniently located on the left hand end of theapron I directly to the left of the handwheel 49. In the bore I04 in theapron I is journaled the rock shaft I 05 against axial movement. On theleft hand and of the rock shaft I05 is provided a bifurcated portion I06having a transverse slot formed therein by the faces I01, I08, and I09.The control handle I03 has a squared portion IIO which is adopted to fitnicely between the faces I01 and I09 and is pivotally mounted on the pinI II passing diametrically through the bifurcated portion I 06perpendicular to the faces I01 and I09: The purpose of this arrangementis to permit horizontal movement of the handle I03 substantiallyparallel to the axis of the rock shaft I05. It is also to be noted thatthe handle I03 may be moved up and down in a vertical plane as it isconfined between the faces I01 and I09. This causes rotation of the rockshaft I05 in the bore I04 in the apron I.

rock shaft I05 and engaging with its rounded 'outer end II4 a slot H5 inthe shifter rod II6 upon which is fixed the shifter yoke II1 adapted toengage and shift the gear 96 and its clutch IOI for cross orlongitudinal rapid traverse when the lever I03 is accordingly moved tothe left or right in horizontal movement as described. Suitable detentmechanism I I8 is provided to facilitate holding the handle I03 ineither of the horizontal positions selected.

The engagement of the rapid traverse clutch assemblies is afiected by upand down movement of the handle I 03 by providing a gear segment I I9 onthe right hand end of the rock shaft I05 which engages rack teeth I20 onthe top of a horizontally slidable pin I2I carried in the apron I on theunder side of which pin is formed rack teeth I22 which mesh with thegear segment I23 formed on the lever arm I24 of the clutch actuatingyoke I25. This yoke I 25 is pivotally mounted on a trunnion I26 in asuitable bearing I21 provided in the apron I and on a pin I28 fixed in abore I29 in the apron I and has an arcuate slot I30 nicely fitting aboutthe outer race of the self-aligning bearing 90 so that when the leverI03 is moved up or down tilting motion will be produced in the yoke I25and through the selfaligning bearing 90 will cause its inner race toeffect operation of one or the other of the clutch assemblies fortraverse movements in either direction. By the use of this'particulararrangement of leverage in conjunction with the selfaligning ballbearing 90 an unusually efficientand sensitive control of these rapidtraverse motions may be obtained with a minimum of effort and skillrequired on the part of the operator in manipulating the handle I03.

Associated with the lever I03 is mechanism for automatically disengagingthe longitudinal feed hand wheel 49 from the apron, transmissionwhenever the rapid traverse lever is actuated to any rapid traverseposition. Noting particularly Figures I, VI, VII, and VIII, on a rockshaft I3I journaled in the boss I32 of the bracket 541s fixed the leverI33 which has a tension spring I34 attached to its outer end and also tothe projecting end I35 of the pin I28 whereby the lever I33 is normallyresiliently urged in a counter-clockwise direction, Figure VI, by thespring I34. Formed integral with the bifurcated end I06 of the rockshaft I05 is the depending arm I36 in the lower bifurcated end of whichis mounted the roller I31 on the pin I38 fixed therein. In the lever I33is formed a detent notch I39 in which the roller I31 enters when thelever I03 is in neutral position and the rapid traverse clutchassemblies inoperative thus allowing the maximum counterclockwisemovement of the lever I33 and the rock shaft I3I. When the lever I03 isactuated up and down to render said rapid traverse clutch assembliesoperative as described the roller engages the surfaces I40 or I whichcauses the lever I33 and rock shaft I3I to be rotated in a clockwisedirection. To the inner end of the rock shaft I3I is fixed the shifteryoke I42 which engages the clutch collar 59 so that counterclockwiserotation of the rock shaft I3I swings the yoke I42 to engage the clutchcollar 59 with the shaft 51 to connect the hand wheel 49 with the aprontransmission, this being affected when the roller I31 enters the detentslot I39 as shown 3' in Figure VI. When the lever I03 is moved up-o'rdown from the position shown in Figure VI, the roller rides along eitherof the surfaces I40 or I swinging the yoke I42 clockwise, Figure VII,disengaging the clutch collar 59 from the shaft 51 and thusautomatically disconnecting the hand wheel 49 from the aprontransmission whenever the lever I03 is moved to an operative position.

Associated with the longitudinal feed hand wheel is a direct readingindicating dial arrangement which is effective at all times to show theexact amount of longitudinal travel of the carriage both in feeding orrapid traversing movements and irrespective as to whether thelongitudinal feed hand wheel is connected or disconnected from the aprontransmission. This mechanism is best shown in Figures VII, IX, XVII,XVIII, and IHX. A gear I43 fixed to the shaft 51 drives a gear I44 fixedon the shaft I45 appropriately journaled on needle bearings I48 in thebracket 54. Formed integral with the shaft I45 is a gear I41 of the samepitch and number of teeth as the gear I44 which engages and drives thering gear I48 journaled on the hub I49 of the bracket 54. Fixed to thering gear I48 is the dial disc I50 upon the periphery of which isadjustably mounted the graduated thousandth collar I5I which isgraduated as shown in Figure XVIII with divisions to show twothousandths of an inch carriage travel along the bed,

one complete revolution of the collar I5I indicating one thousandthousandths on one inch of carriage travel. The rack pinion 43 and theassociated gears 32, 58, I43, and I48, gears I44 and I41 acting asidlers, are so proportioned as to cause the collar I5I to make onecomplete revolution for one, inch of travel of the rack pinion 43 alongthe rack 41 on the bed 48. Thus the collar I5I accurately indicates theexact amount of carriage travel in thousandths of 'an inch.

In order to indicate the number of revolutions of the collar I5I or thenumber of inches traveled by the carriage along the bed a graduated inccollar I52 is provided which is graduated from zero to twenty inches bysixteenths of an inch.

